There are following marks.
On brake lever: Torpedo Schweinfurt, circle sign, U (above) W (below), Sachs S (logo)
On hub shell: S Sachs (logo) Torpedo Schweinfurt 2.8 (above) 36 (below)
On seat mast: (three crowns) 9 (triangle) 83366M
Thanks for the answer!
According to http://www.torpedo-coasterbrake.com/hub-date.htm “On hubs made from 1975 to 1989, you will find 2 letters on the brake lever. The one above is for the month.”
On my brake lever the letter above (for the month) is U. How to translate it to a certain month, since U is the 21st letter (or 19th excluding J and Q)?